Physical remediation of a contaminated area

Physical remediation of contaminated soil or groundwater in brief:

  • implemented without excavating soil and transferring groundwater (in-situ)
  • methods include thermal methods, pump & treat (P&T), aeration and soil vapour extraction (SVE)
  • hazardous substances are degraded or transformed or their migration is hindered by means of physical reactions
  • short treatment time.

Physical remediation methods are based on the degradation or transfer of contaminants or hindering their migration by means of physical processes. The methods are based on, among others, air flow, water flow, pressure, heat, electrical current, etc. The duration of treatment is usually short and the methods are often effective.

Aeration and soil vapour extraction are typical physical remediation methods for soil and groundwater. In aeration, air is injected into the soil or groundwater, evaporating and removing hazardous substances. In soil vapour extraction, volatile and semi-volatile compounds are removed from the soil or groundwater by vacuum. Vapours to be removed from the soil are treated with, for example, activated charcoal filtration or catalytic combustion.

Thermal combustion uses high temperatures to destroy hazardous substances in oxygenated conditions, while thermal desorption uses lower temperatures to evaporate hazardous substances. Emissions produced by combustion are treated.

Soil flushing involves injecting or infiltrating water into the soil. The water may also contain substances that increase the solubility of hazardous substances. The water solubility of hazardous substances is also exploited in soil flushing. The pump & treat method can be used in the treatment of soluble hazardous substances. In pump & treat, water containing hazardous substances is pumped to a treatment plant, from which it is returned to the environment or sent for further treatment to a wastewater treatment plant.

When washing excavated soil, fine soil particles are separated from heavier ones, thus concentrating hazardous substances in a smaller volume of soil. In soil washing, separation may be based on particle size, density, surface properties or combinations of these. A fraction containing hazardous substances (i.e. wash reject) often requires further treatment using other methods, and the remediated fraction can be used at the site.

In electrokinetic methods, hazardous substances, chemicals and water are migrated to electrodes using electrochemical and kinetic processes, thus resulting in chemical reactions. The method is based on the placement of charged electrodes into the ground, with electrical current flowing between them.